Tag Archives: Dagger

A handout picture released from researcher Nathaniel Dominy shows a human thigh bone dagger attributed to the Upper Sepik River (up) and cassowary bone dagger attributed to the Abelam people (down). Credit: Dartmouth College.

New Guinea warriors used human bone daggers — and these are remarkably strong

For centuries, New Guinea natives have crafted bone knives and daggers used for hunting, fighting, and for ceremony. Most are made from the thighbones of cassowaries, which are large, ostrich-like birds. However, some of the daggers are made from human bone — specifically, the thighbone of an ancestor or highly respected member of the tribe — and these are remarkably resilient. In fact, some scientists actually measured the strength of human bone daggers and compared them to the cassowary variety, finding the former is almost twice as strong.

A handout picture released from researcher Nathaniel Dominy shows a human thigh bone dagger attributed to the Upper Sepik River (up) and cassowary bone dagger attributed to the Abelam people (down). Credit: Dartmouth College.

A handout picture released by researcher Nathaniel Dominy shows a human thigh bone dagger attributed to the Upper Sepik River (up) and cassowary bone dagger attributed to the Abelam people (down). Credit: Dartmouth College.

New Guinea tribes are no strangers to weird and peculiar traditions, to use a euphemism, at least to us westerners. Take the Edoro, for instance, an ethnic New Guinea tribe whose range comprises the southern slopes of Mt. Sisa, and who are famous to anthropologists for the ritual pedophilic homosexual acts they practice. The Etoro believe that young boys must ingest the semen of their elders daily from the age of 7 until they turn 17 to achieve adult male status and to properly mature and grow strong. What’s more, among the Etoro, heterosexual intercourse — which they believe makes men die early — is prohibited for up to 260 days of the year and forbidden in or near their houses and vegetable gardens. In contrast, homosexual relations — which the Etoro believe prolong life — are permitted at any time.

A more widespread practice among New Guinea tribes is crafting bone daggers. Nathaniel Dominy, a professor of anthropology at Dartmouth College, got the idea to investigate such weapons after he came across an impressive stash of daggers at the university’s Hood Museum of Art, which were carved out of cassowary and human thighbones. These were like exquisite works of art, featuring elaborate motifs carved into them.

Dominy claims that the daggers were used to kill or finish off victims wounded with arrows or spears, by stabbing them in the neck. There are also accounts from the 1800s and early 1900s that the bone daggers were used for mutilation and cannibalism, but such statements are difficult to verify. Dominy says that these old accounts made by outsiders, such as missionaries, are prone to exaggerations and cultural misinterpretations.

What’s certain, the researchers say, is that the manufacturing of the human bone dagger had a deep cultural significance. Typically, such a dagger was fashioned out of the thighbone of a very important person in the community, either the father of the warrior or some other respected person in the community. This way, the warrior carried the rights and power of the person from which the bone came.

“The human bone dagger is stronger because men gave it a slight different shape—it has greater curvature,” Dominy told AFP.

“We believe that such a shape was done deliberately to minimise the chance of the dagger breaking during fighting. And the reason that men engineered human bone daggers to resist breaking is because human bone daggers carried a lot of social prestige.”

Closeup of a terryfing cassowary claw -- the real life, modern-day Velociraptor. Credit: Featured Creature.

Closeup of a terrifying cassowary claw — the real life, modern-day Velociraptor. Credit: Featured Creature.

The most common type of New Guinea dagger, however, is made from the cassowary. Although it might look relatively harmless, don’t let its appearance deceive you — this is one of the most dangerous birds in the world. It’s the second heaviest in the world after its cousin, the ostrich, and each of its feet boasts a razor-sharp claw that can grow to 4.7 in. (12 cm) in length. With an agile kick, a predator can be easily maimed or killed. What’s more, the bird can jump almost 5 feet (1.5 m) high and can run up to 31 mph (50 km/h). So, it’s not very surprising that New Guinea locals used the cassowary’s claw to fashion daggers out of.

In order to see which of the types of daggers is stronger, the researchers performed computed tomography (CT) scans of five cassowary daggers and five human-bone daggers. The scans enabled the researchers to determine the density of each dagger. Apparently, both types of bones ‘are equally good for making daggers.’ However, when an additional cassowary-bone dagger — which was bought especially for this study — was destroyed in a bending test to see how much force it could take before breaking, the weapon proved far inferior to the human bone one. The test showed that the bird bone weapon could handle up to 44 lbs (200 newtons) of force before breaking, while the human bone dagger could withstand twice as much force. The researchers say that it’s likely that the human daggers are stronger because they crafted with greater care, seeing how they were a lot rarer and more valuable than the bird-bone daggers.

The findings were reported the journal Royal Society Open Science.

Bacteria knives

Scientists use the world’s smallest chisel to investigate dagger-wielding bacteria

A new paper describes how one species of bacteria learned to not only stay safe but profit from their greatest enemies, amoeba. The secret is wielding a lot, a lot of knives.

Bacteria knives

Image credits me / ZME Science.
Free to use with attribution.

Bacteria usually steer as clear of amoeba as they possibly can — because amoeba like to snack on them. They’re bigger and usually faster than bacteria, and will envelop any they can catch in pseudopodia to be digested at a later date. Not the nicest of fates.

Some of the bacteria have learned to defend themselves in pretty spectacular ways. One such species is known as Amoebophilus, and was discovered by researchers at the University of Vienna a few years back. It doesn’t only survive inside amoeba but is so well adapted to thrive in there that they’ve have become this species’ favorite habitat.

Now, working together with the Viennese researchers that discovered the bacterium, scientists from ETH Zurich have uncovered the mechanism that guarantees the bug’s survival inside amoeba. And it would make Arya Stark proud: the bacteria has (possibly poison-coated) dagger-launcher devices built into its membrane that allows it to shred their predators from inside and avoid digestion.

Bringing a knife to a bug fight

To find the bacteria’s secret, the researchers used a novel method developed at ETH that’s currently in use only in a handful of labs worldwide. They froze amoeba that had absorbed bacteria at minus 180°C (-292°F). Then João Medeiros, a doctoral student at ETH and paper co-author, used a focused ion beam to cut away at the specimens, much like archaeologists chip away at soil and rock around an artifact with chisels. After milling away the amoeba and most of the bacteria, Medeiros was able to extract the bug’s defensive mechanism and produce a three-dimensional electron tomogram of it.

The mechanism consists of several sheaths affixed onto the bacterium’s inner membrane by a baseplate and an anchoring platform. Their purpose is to shoot molecular-sized “daggers” at the amoeba. Each sheath “is spring-loaded and the micro-dagger lies inside it,” explains João Medeiros, a doctoral student at ETH and paper co-author.

Clusters of daggers.

A cluster of the spring-loaded daggers inside Amoebophilus. Green ones are ‘loaded’, red shows them after the dagger has been launched.
Image credits Leo Popovich / ETHZ.

“When the sheath contracts, the dagger is shot outwards extremely quickly through the bacterial membrane.”

This comes in really handy for the tiny Amoebophilus, as amoeba surround their pray into a stomach-like digestive vesicle (a pocket of membrane inside the amoeba filled with digestive fluids). The daggers shred through these vesicles and allow the bacteria to escape the very unfriendly conditions of the digestive bubble. But it doesn’t escape all the way — once safe, Amoebophilus stays inside the amoeba and takes advantage of its host to feed and even multiply.

We don’t really know why these digestive vesicles get destroyed so easily. It may be that it’s simple mechanical force that does it, but the team suspects there’s more at play here. Their theory is that Amoebophilus’ daggers are also coated in ‘poison’ in the shape of membrane-degrading enzymes. The theory looks to be right, based on bits of genetic code that researcher at the UOV have shown to encode information for such enzymes.

Tiny stabbings

It’s not the first time we’ve seen such daggers in biology. Bacteriophages, viruses which specialize in preying on bacteria, use similar systems to inject their genome past their defenses. Some species of bacteria are known to use similar micro-weapons to pepper their surroundings in ‘ow’ and deter competing microorganisms from a source of food, for example.

What sets these findings apart is the sheer fidelity and resolution the team managed to get on the mechanisms. They’re also the first to create the complete 3D structure of such mechanisms inside cells in their natural context and the first to show the details in the baseplate and membrane anchor.

“In the past, cell biologists investigated the function of such systems and structural biologists elucidated the structure of individual components,” says ETH Professor Martin Pilhofer, the paper’s corresponding author.

“With the cryo-focused ion beam milling and electron cryo-tomography technologies that we have established at ETH Zurich, we can now close the gap between cell biology and structural biology.”

Another new discovery the team can boast is finding these mechanisms arranged in clusters. All previous known micro-dagger weaponry we’ve found is deployed as individual devices. Amoebophilus, however, is not shy of escalating the conflict, using heavy batteries or clusters of up to 30 dagger-launching systems.

“You could call them multi-barrel guns,” Pilhofer adds.

The team also used genomic comparisons to peek into how Amoebophilus evolved its daggers. Their results show that “the relevant genes are very similar to bacteriophage injection systems,” which led the team to believe that these genes are originated from an ancestor of today’s bacteriophages that left bits of its code in the bacteria’s genome long ago. The results also suggest that many other bacterial strains in at least nine of the most important groups should have similar dagger arsenals. It’s not yet known whether they serve the same purpose or not, but the team says their next steps will be to find out.

They also plan to use the new method of cryo-focused ion beam milling to look at other complex molecular systems.

The full paper “In situ architecture, function, and evolution of a contractile injection system” has been published in the journal Science.